1. Field of the Invention
The present invention relates to a printer having two or more interfaces, and more particularly to a printer connected to an external host device having a plurality of peripheral devices.
2. Description of the Related Art
In department stores, supermarkets, hotels and the like, POS (point of sale) systems for sales management are installed at cash counters where goods and cash are handled and settled. A POS system usually includes one host device, and a plurality of peripheral devices connected thereto, such as a printer, a bar-code reader and a magnetic card reader.
A recent trend has been toward increased types of peripheral devices to cope with diversified data input and data output methods for handling product codes and credit numbers. This requires an increase in the number of interface terminals mounted in the host device.
FIG. 6 is a block diagram showing one example of conventional POS systems. One of a variety of commercially available personal computers is often used as a host device H in order to save cost. The personal computer usually has one or two serial ports, and one parallel port. Thus, a maximum of three peripheral devices, i. e. devices Q1 and Q2 and a printer P, may be connected to the host device H. The host device H lacks a connection port for connecting a fourth peripheral device Q3 or more peripheral devices.
For connecting more peripheral devices than the number of ports of the host device H, an expansion board must be added to the host devices H to provide an increased number of ports. However, not only the cost of the expansion board itself, but a complex control program is required for controlling the expansion board. This results in an increase in the cost and an extended period for development of the entire POS system.
A scanner/printer connectable to a computer is known, in which an optical scanner and a printer are integrated to provide a fax function and a copying mechanism. However, this is a stand-alone type with a particular scanner mounted in a printer, and has no expandability for connecting other peripheral devices.
Japanese Unexamined Patent Publication JP-A8-123640 (1996) describes a connection switch mechanism provided between a host device having only one interface and a plurality of printing devices, for distributing signals by switch circuits on signal lines. This mechanism requires a complicated and costly switching circuit for switching a data bus and a control bus having a plurality of signal lines. Moreover, the mechanism is applicable only to parallel communication based on a busy signal.